Above, Fred, I was suggesting that the paw-word might have been a doggy-distraction from the oral activity rather than a notion that the distinct body-parts should be brought together!
How about this, then?...
Since the 16th century, the word 'peg' has been used to mean a tooth. Both Peg and Meg are diminutives of the name, Margaret, and thus effectively synonymous. Could it, therefore, be that meg = tooth is just a very local - or even just family - dialect creation? At one time, my whole family referred to our Alsatian as 'the vog' rather than 'the dog' because I - for some insane reason - started to call him that.